Was rooted a while ago (software update disabled with methods listed on this site... a year go).
Then "something happened", widgets gone, root gone. (well, can't FTP or telnet to it).
Tried resetting smart hub, widgets gone, still can't login as dev, or open anything.

Tried method in OP (created InstallSamygo/data on a FAT32 USB, put 128.xfs file into it, plugged it into TV, switched it on).

If hotplugging it asks what kind of content it is, Video, Images or Music.

This is normal. Press the back button and look in SH.
the image is not clear but it seems not what it should be.
Look carefully al first post of this discussion:
- download InstallSamygo_1_1_E.rar
- unpack it to USB root formatted FAT32
- copy samyext4.img to InstallSamygo/data on USB (together with empSmG,libSmG.zip,rcSGO,RestoreSmG.zip,SamyGO.zip)

This is normal. Press the back button and look in SH.
the image is not clear but it seems not what it should be.
Look carefully al first post of this discussion:
- download InstallSamygo_1_1_E.rar
- unpack it to USB root formatted FAT32
- copy samyext4.img to InstallSamygo/data on USB (together with empSmG,libSmG.zip,rcSGO,RestoreSmG.zip,SamyGO.zip)

Oh, missed the E.rar attached to the post. (samyext4.img is not for E series)
Still no effect though...

But I didn't tried it yet...
Maybe Samsung is trying to push us to latest fw.... What the f...
As it looks like that happens only to older ES or EH models from 2012....

I don't even want anything besides installing some widgets. But what I am afraid of is that I'd upgrade firmware, Samsung's shit won't work and I will lose ability to root and put widgets on it manually...

In a F series i have some freezing problem. I have changed the:
"To prevent possible overfilling of samyext4.img on F-series, once rooted it is necessary to edit /mnt/etc/init.d/01_01_catch_crap.init : find string "echo "+++++++++++ Release notes ++++++++++" >> $LOGFILE" and change ">>" to ">"."

Is there anything else i can change in order not to have logs to fill the image ?